In a closed circuit fuel system such as employed with aircraft, a fueling nozzle is firmly attached to a fuel tank inlet in a fluid-tight and mechanical manner wherein a sealed relationship exists between the nozzle and the tank inlet. Such systems are used with "under-wing" fuel inlets, and the fuel is forced into the fuel tank under pressure.
With fuel systems of the closed circuit type, it is critical that the nozzle be firmly attached to the tank inlet in a sealed manner, the nozzle must include effective seals to prevent leakage, the operation of the nozzle components must be positive and safely operable, fluid flow through the nozzle must not occur until proper attachment with the tank inlet has been made, fuel flow through the nozzle must be relatively unrestricted and the pressure should be regulated protecting fuel system components from high pressure fuel, and the nozzle should automatically close upon the fuel tank being filled.
While fueling nozzles for closed circuit sytems are available which meet some of the aforementioned prerequisites, there is a need for a closed circuit nozzle which overcomes the disadvantages of nozzles presently available. For instance, available closed circuit fueling nozzles are prone to sealing and leaking problems. Many of these problems may be attributable to the fact that the interior of the nozzle is subjected to the maximum fuel pressure of the fuel supply system when the nozzle is not in use. Also, pressure regulation and automatic shut off are not as dependable as desired and the condition of the pressure regulating components are not discernible by the operator.
Fueling nozzles of the closed circuit type often incorporate springs located within the fluid flow passage and there is the possibility that spring fractures would permit particles to enter the fuel system. Other deficiencies present in available closed circuit nozzles exist in the operation of the various nozzle components wherein undesirable rotation of the manually operated locking sleeve creates problems.
It is an object of the invention to provide a closed circuit fueling nozzle having improved sealing characteristics at dynamic surfaces, and wherein long effective seal life is achieved.
Another object of the invention is to provide a closed circuit fueling nozzle which automatically prevents fluid flow therethrough until the nozzle is properly mounted upon the tank inlet, and improper connection of the nozzle to the inlet, or unintentional nozzle disconnection, automatically closes the nozzle.
A further object of the invention is to provide a closed circuit nozzle incorporating a pressure regulator wherein the regulator controls the pressure of the fuel within the nozzle passage, and the primary portion of the nozzle passage is only subjected to regulated pressure.
An additional object of the invention is to provide a closed circuit fueling nozzle having a positive latching mechanism for attaching the nozzle to the tank inlet, and wherein the latching mechanism is sensitive to the alignment and connection to the tank inlet and will not permit coupling until proper alignment and interconnection has been achieved.
Yet another object of the invention is to provide a closed circuit fueling nozzle employing a pressure regulating spring-biased sleeve wherein the spring is isolated from the fuel flow path, and indicating means are defined on the nozzle sensing the position of the regulator sleeve and visually indicating to the operator the position and condition of the sleeve.
In the practice of the invention the nozzle includes a body in which an elongated passage is defined. The passage includes an inlet end, and an outlet end in axially spaced relationship to the inlet end. A fuel supply hose is attached to a supply channel defined in the body which selectively communicates with the passage.
An elongated plunger concentrically located within the body passage is axially positionable therein between extended and retracted positions by a manually operated handle through a rack and pinion drive. The plunger includes an enlarged head disposed adjacent the passage outlet end, and a chamber formed in the body concentric to the plunger receives a piston mechanically connected to the plunger. The chamber communicates with the passage and fluid pressure acting on the piston balances that pressure tending to force the plunger head in the opposite direction.
An annular valve sleeve located within the body passage inwardly of the plunger head is spring biased toward the head for sealed engagement therewith. The valve sleeve is also accessible from the passage open end and is held in an open position by the fuel tank inlet structure. The plunger is used to open a self-closing valve in the tank inlet and the valve sleeve will automatically engage the plunger head to seal the body passage outlet end when the nozzle is removed from the tank inlet.
An elongated annular axially displaceable pressure regulating sleeve is located within the nozzle body passage intermediate the inlet and outlet ends. The regulator sleeve includes differential area pressure faces exposed to the fuel pressure, and is biased by a spring in a direction away from an annular valve seat defined in the passage adjacent the inlet end and fuel supply. The open annular end of the regulator sleeve functions as a valve directly engagable with the valve seat, and as the regulator sleeve is sealed with respect to the body passage, engagement of the regulator sleeve with the valve seat seals the body passage with respect to the fuel supply channel preventing most of the interior of the nozzle from being exposed to the maximum fuel pressure existing within the supply channel.
The spring for the pressure regulator sleeve circumscribes the sleeve and is isolated from the fuel flow therethrough. As the regulator sleeve is always exposed to the fluid pressure within the body passage the sleeve will position itself to the valve seat to achieve the desired predetermined pressure as controlled by the relative areas of the differential pressure faces and the characteristics of the spring.
An axially displaceable rod is mounted within the body which engages the pressure regulator sleeve as the sleeve approaches its valve seat, and the rod includes a lost motion connection with an outer end which is visually observable whereby the operator is immediately advised of the position and condition of the regulator sleeve.
A manually operated locking sleeve reciprocally mounted on the exterior of the body adjacent the passage outlet end cooperates with pivotal latch fingers which grip the tank inlet to maintain the interconnection between the tank inlet and nozzle. Release pins mounted on the body adjacent the passage outlet end engage the tank inlet to automatically release detents which restrain the locking sleeve against movement in the locking direction until proper alignment and positioning of the nozzle and tank inlet has been achieved.